/Engine/Source/Editor/MeshPaint/Public/MeshPaintHelpers.h
Given the adapter, settings and view-information retrieves influences triangles and applies Action to them
static bool ApplyPerTrianglePaintAction ( [IMeshPaintGeometryAdapter](API\Editor\MeshPaint\IMeshPaintGeometryAdapter) * Adapter, const FVector & CameraPosition, const FVector & HitPosition, const [UPaintBrushSettings](API\Editor\MeshPaint\UPaintBrushSettings) * Settings, FPerTrianglePaintAction Action )